The present invention relates to a process for modifying, by mild oxidation, the swelling properties of a swelling coal with an AFNOR swelling index of between 2.5 and 6, such as a high volatile bituminous coal, as well as to an installation for carrying out the process and to a chamber for treatment by fluidisation and crushing.
The production of semi-coke in a rotating oven or in a fluidised bed from fines involves the use of sparingly swelling coal so as to avoid sticking and agglomeration of the fines. Similarly, for manufacturing moulded coke, it may be desirable to have coal with a low swelling index.
French Pat. No. 1 332 711 already proposes oxidising the fines by fluidisation, with considerable recycling of the finest particles, in a bed of which the temperature is greater than 300.degree. C. and lower than the melting temperature of the coal, by means of a gas containing oxygen, for example by combustion gases at 450.degree. C. containing 18% of oxygen. The fact that the fines of coal are previously crushed in practice obliges the temperature of the combustion gases to be limited to about 450.degree. C. to avoid a loss of volatile matter, too much degradation and a beginning of softening and therefore sticking of the finest particles.
It is an object of the invention to propose a novel process, a novel installation and a novel chamber for modifying the swelling properties of the swelling coal whilst substantially conserving their content of volatile matter, and consequently to allow such coal to be used for manufacturing moulded coke or semi-coke in a rotating oven or in a fluidised bed. It is a further object to avoid the degradation of the treated coal whilst using hotter gases, therefore with faster effect.